The disclosure generally relates to an AC-DC power converter and, more particularly, to the control circuit of the AC-DC power converter which may sustain high voltage.
Along with the depletion of the energy, many industrial standards require the electronic products to utilize the energy more efficiently. In many electronic products, the AC-DC power convert is utilized to convert the input power signal to suitable output voltage signals or output current signals for providing power to the load. Improving the energy efficiency of the AC-DC power converter is therefore an important topic.
The control circuit of the AC-DC power convert may detect the input power signal and configure the AC-DC power converter to operate in a suitable operation mode. For example, when the control circuit does not detect the input power signal, the control circuit may discharge the EMI suppression capacitor to prevent the users from electric shocks and comply with the safety standards
The control circuit therefore must be directly coupled with the input power signal to accurately configure the AC-DC power converter to the suitable operation mode. The voltage value of the input power signal, however, usually ranges from 90 volts to 270 volts, and may be even higher. When the control circuit is directly coupled with the input power signal, the control circuit must sustain 400 volts or higher DC signals (e.g., 700 volts is commonly required in the industry). When the control circuit is realized with integrated circuit, the control circuit usually may not sustain such high voltage signals.
In the U.S. Pat. Nos. 7,306,999; 7,638,405; 7,803,643; 7,955,943 and 8,283,705, several control circuits for the AC-DC power converter are disclosed. The control circuits utilize a high voltage detection circuit to detect the input power signal. When the control circuits are realized with integrated circuit, the circuit layouts of the resistors and other circuit elements must be carefully designed. Otherwise, the circuit elements are vulnerable because of the variations in the circuit layout or the variation of the semiconductor fabrication. The hardware complexity of the control circuit is greatly increased and the yield of the control circuit may not be easily enhanced.